On a fresh install of Vista, you will get the following warning every time you try to connect to a Windows 2003 server using Remote Desktop included in Vista (which is Remote Desktop version 6.0.6000.16386):

Remote Desktop cannot verify the identity of the computer you want to connect to.

If you are in a work environment where you trust the Windows 2003 servers you connect to, you can safely remove this warning by adding an entry to your Vista machine's Registry:

1. Open Regedit

   

    

2. Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Terminal Server Client
3. Add The DWORD (32-bit) Value AuthenticationLevelOverride and give it the value 0

   

Your entry should look like this:

That's it! No need to restart or logout; you can just open a new remote desktop connection to test your changes.